Some platforms (e.g. FreeBSD) do not have libdl, but dlopen and related
functions are part of libc. So first check for dlopen in libc, and only
if that fails, look for it in libdl.
Task-number: QTBUG-52951
Change-Id: I65a8ed18fce157da32f4e1ffeba30d7513385a8f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
-ldl option was used unconditionally while libdl is not supported
when libc is static.
Add build test to configure which checks if libdl is supported.
QMAKE_LIBS_DYNLOAD in "src/corelib/plugin/plugin.pri" is now used only
if libdl is available.
qt_linux_find_symbol_sys from qlibrary_unix is now used only if
QT_NO_DYNAMIC_LIBRARY is not defined.
Initially reported by Buildroot autobuilder here:
http://autobuild.buildroot.net/results/a85/a85a1839a45fb6102e53131ecc8f6dadf92bcdc2
Change-Id: I0397472456efdc4f3ab5f24d01253bee8048a9d1
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>